haem

Definitions

from Wiktionary, Creative Commons Attribution/Share-Alike License

n. The component of haemoglobin responsible for binding oxygen, consists of an iron ion that binds oxygen and a porphyrin ring that binds the globin molecules; one molecule binds one molecule of oxygen.

Most striking was the finding that depletion of haem, and addition of GSSG or dsRNA all seemed to have similar effects on cell-free protein synthesis in the reticulocyte lysate, as though these disparate agents all acted in a similar manner.

Together with Tony Hunter, a fellow student, I became interested in the question of when the haem was inserted into globin to make haemoglobin, and the question of whether ribosomes had to queue up under conditions where iron (and hence haem) was limiting.

It took three or four years to realise that this inhibition was due to the action of at least two inhibitors of the process, one activated by the absence of haem, the other by the presence of dsRNA, and that these inhibitors were protein kinases, which phosphorylated eIF-2, the key initiation factor that catalysed the binding of